Sheared Bolts

[RogerJ]

I have a wood burning stove for which I need to replace an internal back-plate that is held in place by 4 small bolts. The four bolts came of very easily - so easily in fact that the heads sheared on all four with hardly any effort!!

So the question is how I can remove the studs remaining? If I could drill them out then it would not be a problem but my normal bits won't seem to touch them - the ends just get red hot with hardly any impression on the stud. Any ideas or do I have a rather large door stopper?

 

[clift_d]

Is there any of the stud protruding and if so could you try welding a nut on the end? Just thread the nut onto the stud, back it off half a turn and then weld the top of the stud to the inside of the nut to form a new head. Give it a moment or two to cool down and then put a spanner on it - just try to get it moving a little at first, then a bit more etc until you are able to turn it out.

 

[Rocketman]

Brand new carbide drills should be able to do it.

 

[BrokenBiker]

another vote for carbide, but they have to be sharp and good condition.

 

[Cobbler]

Is there any of the stud protruding and if so could you try welding a nut on the end? Just thread the nut onto the stud, back it off half a turn and then weld the top of the stud to the inside of the nut to form a new head. Give it a moment or two to cool down and then put a spanner on it - just try to get it moving a little at first, then a bit more etc until you are able to turn it out.

As an addition to the above, if broken almost flush, countersink a nut the full depth so it sits over the remaining bolt, then fill it with weld, usually the heat from the weld will break down the corrosion & it will unscrew. It doesn't matter what thread of nut you use as you are countersinking it right through.

 

[gordon stephenson]

I would imagine a solid carbide drill will be quite expensive and also the cutting edges are very brittle,For jobs like yours (if I can't weld a nut on top ) I have some triangular Diagrit drills designed to drill out broken taps etc. Good luck.

 

[clift_d]

Is there any of the stud protruding and if so could you try welding a nut on the end? Just thread the nut onto the stud, back it off half a turn and then weld the top of the stud to the inside of the nut to form a new head. Give it a moment or two to cool down and then put a spanner on it - just try to get it moving a little at first, then a bit more etc until you are able to turn it out.

A bit like this:

 

[julianthegypsy]

I've done more than my fair share of repairs to stoves, which always involve sheared bolts. You'd think they'd have figured out by now that after a few years in service these stupid little bolts will always rust solid and shear off, but apparently not. When it happens to me I just grind it back flush, centrepunch it as close to centre as I can then drill it out with a normal hss drill. Sounds like you might have been going too fast if your drill is getting hot. Once drilled I either tap it out to the next size up or drill right through and put a nut and bolt on, whichever seems most appropriate at the time. I always use stainless replacements. I also dismantle enough so I can get it under a bench drill as well, it would be much harder using a hand held.

 

[Rocketman]

I've done more than my fair share of repairs to stoves, which always involve sheared bolts. You'd think they'd have figured out by now that after a few years in service these stupid little bolts will always rust solid and shear off, but apparently not. When it happens to me I just grind it back flush, centrepunch it as close to centre as I can then drill it out with a normal hss drill. Sounds like you might have been going too fast if your drill is getting hot. Once drilled I either tap it out to the next size up or drill right through and put a nut and bolt on, whichever seems most appropriate at the time. I always use stainless replacements. I also dismantle enough so I can get it under a bench drill as well, it would be much harder using a hand held.

Sounds spot on how I would do it bar the last bit. Stainless bolts are known for seizing in steel - a good reason to avoid using them on engine blocks. I would instead go with high tensile bolt and use anti seize copper grease on it instead.

 

[julianthegypsy]

Sounds spot on how I would do it bar the last bit. Stainless bolts are known for seizing in steel - a good reason to avoid using them on engine blocks. I would instead go with high tensile bolt and use anti seize copper grease on it instead.

Now that I didn't know. Thank you, something to remember for next time.

 

[RogerJ]

Thanks very much all - I'll give one or more a try. Three of the bolts have some protrusion but the fourth is flush.

 

[BrokenBiker]

regardless of drill size above 5mm I always use a slow speed. below 5mm I start getting a bit quicker and then anything below 3mm is fastest speed I have

 

[500e]

Sandvic also do Carbide drills quality products

 

[MattF]

regardless of drill size above 5mm I always use a slow speed. below 5mm I start getting a bit quicker and then anything below 3mm is fastest speed I have

Slow speed works well with small bits too, not just the larger ones. With a situation like the above, keeping it slow no matter the drill bit size, (the bit being sharp is a necessity though), works well. Speed just generates heat.

 

[BrokenBiker]

I usually find that the smaller bits snag at low speed and snap, a quicker speed has always worked for me on drills smaller than 3ish mm

 

[MattF]

Nah, you're just being an ape with them. The small bits are a doddle to snap if you're not careful. Never had one snap for any reason barring operator error though, (read that as I inadvertently applied sidewards pressure ), and even then I can only recall snapping very few in god knows how many years.